1. Field of the Invention
The present invention relates to an apparatus having an image processing system for recognizing road environment, and particularly, to an apparatus employing an image recording unit such as a television camera mounted on a car, for recognizing traffic lines such as white lines painted on a road and a car running ahead.
2. Description of the Related Art
Although car technology is improving, traffic accidents are increasing. Many traffic accidents are caused due to human errors in judging situations. It is desired to develop apparatuses for assisting human vision.
Driver assisting apparatuses employing image record units such as television cameras recognize road conditions and a car running ahead.
When driving a car, a driver must follow white or yellow traffic lines painted on a road and must be careful about the movement of a car running ahead.
The traffic lines are important to control traffic and guide cars. Drivers must follow the traffic lines.
An apparatus for recognizing the traffic lines alerts a driver if the car runs out of a lane and controls the car according to the recognized information. This will reduce the load on the driver and prevent traffic accidents.
Drivers must be careful about the movement of a car running ahead. An apparatus for recognizing the car ahead alerts the driver if the driver's car runs out of a lane, or if the car ahead comes dangerously closer to the driver's car and controls the car to follow the car ahead. This will reduce the load on the driver and prevent traffic accidents.
FIG. 26 shows an apparatus for recognizing road environment according to a prior art.
This apparatus has an image recording unit, i.e., a television camera 1 for picking up a road image, an edge image extraction unit 2 for providing an edge image showing contours of objects according to the road image, a unit 3 for extracting edges of traffic lines 6 according to the edge image, and a unit 4 for calculating the position of each traffic line according to the edges.
Referring to FIGS. 27 and 28, pixels in the road image 5 are scanned from the center of the image 5 in left and right directions as indicated with arrow marks, to find contours 7 and 8 of each traffic line 6. Each position where a scan line intersects the contours 7 and 8 is defined as a traffic line position 9.
If the road image 5 includes a car running ahead or if the traffic line 6 is discontinuous as shown in FIG. 28, the prior art is usually unable to recognize the traffic line 6.
Due to the car 10 running ahead, the prior art is unable to detect the contours 7 and 8 of the traffic line 6 and mistakes a contour 11 of the car 10 for the traffic line 6.
If the traffic line 6 is discontinuous, the prior art will not find the traffic line 6 at discontinuous parts thereof. If the road image 5 involves a shadow 12 of a building or a tree as shown in FIG. 30, the prior art will mistake the shadow 12 for the edges of the traffic line 6.
In actual road environment, the road image 5 always involves obstacles and noise, so that it is very difficult for the prior art to recognize the traffic lines 6.
FIG. 29 is a block diagram showing an apparatus for recognizing a car running ahead according to a prior art.
This apparatus has an image recording unit, i.e., a television camera 1 for picking up a road image, an edge image extraction unit 2 for providing an edge image showing edges of objects according to the road image, a car search unit 20 for two-dimensionally searching for a longest horizontal edge 13 according to the edge image and finding a rectangle according to the edge 13, and a unit 21 for calculating a distance to the car ahead according to a distance table and the center position of the rectangle on the edge image.
If there is a long horizontal shadow 12 on the road as shown in FIG. 30, the prior art will mistake the shadow 12 for a horizontal edge of the car ahead.
If an edge is disconnected due to noise in the road image, the prior art will fail to recognize the car ahead. In an actual road environment, the road image unavoidably contains noise such as the shadow 12, and therefore, the prior art may not recognize the car running ahead.
To recognize the car ahead, the prior art two-dimensionally searches the whole of the road image for a most probable edge. This takes a long time. The prior art is incapable of determining whether or not the recognized car is running in the same lane where the car itself is running.